Reverse valve assembly for fluid-operated downwell pumps

ABSTRACT

A reverse valve assembly for fluid-operated downwell pumps comprising an elongated tubular valve spool, which is longitudinally disposed from the uppermost engine piston and mounted for reciprocal movement in the valve housing, and a longitudinal pilot rod attached to the uppermost engine piston and extending through the valve spool. The valve spool is provided with lands thereon defining annuli communicating with operating fluid under pressure and with discharge, and the pilot rod is provided with interconnecting port means. As the pilot rod reciprocates, the signal for movement of the valve spool is provided through the port means and the area above the uppermost engine piston is alternately pressurized and exhausted, causing the engine to reciprocate.

United States Patent Peter S. Bloudoii Whittier, Calif.

Appl, No. 882,022

Filed Dec. 4, 1969 Patented July 20, 1971 Assignee Armco Steel Corporation Middletown, Ohio Inventor REVERSE VALVE ASSEMBLY FOR FLUID- OPERATED DOWNWELL PUMPS 35 T 4? 5r 48 .1 38 34 23 44 Z 24 60 I 33 t; 68 J 70 a 4c a E r3 \1 2: l b K7 J 26 my? 40 OPERATING rum) DISCHARGE [56] References Cited UNITED STATES PATENTS 2,82l,l4l 1/1958 Sargent 9l/3l3X 2,983,227 5/l 96l English 91/224 X Primary Examiner-Robert M. Walker AttorneyMelville, Strasser, Foster & Hoffman ABSTRACT:' A reverse valve assembly for fluid-operated downwell pumps comprisingian elongated tubular valve spool, which is longitudinally disposed from the uppermost engine piston and mounted for reciprocal movement in the valve housing, and a longitudinal pilot rod attached to the uppermost engine piston and extending through the valve spool. The valve spool is provided with lands thereon defining annuli communicating with operating fluid under pressure and with discharge, and the pilot rod is provided with interconnecting port means. As the pilot rod reciprocates, the signal for move ment of the valve spool is provided through the port means and the area above the uppermost engine piston is alternately pressurized and exhausted, causing the engine to reciprocate.

PATENTEU'JULZOIQYI SHEET 2 [IF 4 FIG-2 w OPERATIIJG FLUID DISCHARGE INVENTOR/S PETER S. BLOUDOFF ATTORNEYS PATENTED JUL 20 1971 SHEET 3 BF 4 FIG-3 OPERATING FLUID f DISCHARGE lNVENTOR/S PETER s. BLOUDOFF BY /zadm, L/CC .44/1 and Wild)! ATTORNEYS PATENTED JUL 2 0 I97:

SHEET 4 [IF 4 4 H an.) 1 H 1?.21 I

INVENTOR/S PETER S. BLOUDOFF FIG-6 OPERATING FLUID E G R A H C B D BY L 6 0440, aI/a ATTORNEYS REVERSE VALVE ASSEMBLY FOR FLUID-OPERATED DOWNWELL PUMPS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to fluid operated downwell pumps and is particularly directed to improvements in the control valves for operating engines employed in such pumps.

2. Description of the Prior Art It is becoming increasingly rare when the plans for the producing phase of an oil field do not include a water flood. Often water injection is begun immediately as a means of maintaining bottom hole pressures and thereby extending the flowing life of the field. In any case, as a well of this type goes on the pump, it can be assumed that large quantities of water will have to be produced with the oil and that the total volumes to be pumped will gradually increase as the percentage of water increases. Hydraulic downwell pumps disposed at the lower ends of deep wells are especially suited to these installations, as their capacity may be controlled by varying their speed, and this being effected by simply adjusting valves to control the volume of power fluid being provided to the particular well. An additional advantage of hydraulic pumps is being able to retrieve a free-type hydraulic pump by circulating it out of the well. Such retrieval becomes even more important due to the short life of equipment which results from the adverse environment which is often encountered in water flood walls.

Since the casing size of a well will generally limit tubing size used therein, such as for example, to 2% inches, there is definitely a limitation on the size of downwell hydraulic pumps which may be utilized within the casing, and thus upon the potential capacity thereof. While the capacity of such downwell pumps may be increased by using engines and pumps in tandem, it has been found, however, that there is a practical limit to the number of engines and pumps which may be used in tandem, this limit generally being what one man can reasonably be expected to handle safely.

The weight and length of a hydraulic pump, to a greater extent than any other factor, are effected by the length of stroke of engine and pump pistons. While a minimum stroke length of, for example, 6 inches and a cycle rate of 360 strokes per minute has been found to be satisfactory in hydraulic pumps which utilize three engine pistons and two pump pistons, it has also been found that in order to attain the cycle rates desired the reversal times must be kept minimal. Prior art reverse valves have generally proven to be unsatisfactory in this connection.

U.S. Pat. No. 2,204,120, issued June II, 1940, for the invention of Clarence .l. Coberly, entitled Liquid Operated Mo- 1 tor, discloses a valve whose switching chamber is effected by an alternating pressure and with the pressure within the switching chamber being supplemented by leakage from an adjacent alternating pressure source. During reversal, relatively large fluid passages are brought into play to promote ingress or egress of pressure into the switching chamber to literally overwhelm the counter force of the fluid being leaked. The rate of leakage is important. For example, if too much leakage is permitted, reversal time is slowed, and if too little leakage is permitted, there is a hazard of plugging and making the circuit inoperable. There is also the further danger of stalling at slow speeds because the switching slots do not open fully to provide sufficient flow to overcome the leakage. Consequently, the downwell pumps utilizing this valve are limited by minimum speeds at which a standard unit will run.

A further example of a prior art reverse valve is disclosed in Pat. No. 2,870,749, issued Jan. 27, I959, for the invention of R. H. Deitrickson, entitled Control Valve For Fluid Operated Engines For Downwell Pumps. The reverse valve of this disclosure is the epitome of simplicity. In this configuration, even the reversals do not require a piloting circuit. However, in

practice these valves have experienced some deacbcentering tendencies which have been difficult to explain and correct. While the idiosyncrasies of these valves may be tolerated in small downwell pumps, their use is unacceptable in larger units.

Still a further example of prior art reverse valves is disclosed in U.S. Pat. No. 3,050,038, issued Aug. 21, 1962, for the invention of Peter S. Bloudoff, entitled Valve Mechanism For Fluid Operated Downwell Pumps. Here the reverse valve is switched by a pilot means at one end of the stroke and allowed to switch by becoming unstable at the other end. While the valve is disclosed as bcing within a piston, which is its optimum position, a stationary version which is actuated through a 'pilot rod traveling with the piston is also in use.

SUMMARY OF THE INVENTION In its broadest concept, the present invention provides a reverse valve for a fluid operated downwell pump which uses a pilot rod having ports therein to promote a full switch and to prevent drift thereof. In particular, the reverse valve of the present invention is more positive. That is to say, the valve is held in position until ready to switch, while at the same time it will tolerate appreciable leakage across the lands thereof as well as more imbalance, wear and contamination. In summary, the reverse valve of the present invention allows the engine cycle rates to go up markedly, with a more positive reversal.

More particularly, the present invention provides a reverse valve assembly for fluid operated downwell pumps comprising an elongated tubular valve spool having first, second and third lands, the second land being the largest of the three. The valve spool is longitudinally displaced from the uppermost engine piston and mounted for reciprocal movement in the valve housing. The valve spool is provided with a first annulus between the first and second lands and with a second annulus between the second and third lands, the first annulus being approximately twice the area of the second annulus. The second annulus is always in communication with operating fluid under pressure and the interior of the valve spool is always in communication with an exhaust passage or discharge.

Port means are provided communicating with the area above the uppermost engine piston and alternately connect this area with the second annulus and with the interior of the valve spool. Additionally, a longitudinal pilot rod extends through the valve spool and is attached to the uppermost engine piston for movement therewith. The pilot rod is provided with three sets of spaced apart radial ports therein which are interconnected through passage means.

In operation, movement of the valve spool is signaled as the pilot rod reciprocates, the first set of ports moving between communication with the operating fluid and communication with the first annulus, the second set of ports moving between communication with the first annulus and communication with the interior of the valve spool, and the third set of ports moving from a first closed position through an open position in communication with the area above the uppermost engine piston to a second closed position, respectively. As the valve spool is moved back and forth in the valve housing, the third land thereof alternately connects the port means, and thus the area above the uppermost engine piston, with the second annulus and with the interior of the valve spool. This alternately pressurizes and exhausts the area above the uppermost engine piston and thereby causes the engine to reciprocate.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partial vertical elevational view of a downwell pump with parts broken away and in vertical section.

FIG. 2 is a central vertical sectional view, with parts broken away, of a hydraulic motor in the downwell pump of FIG. 1, having a valve spool mechanism constructed in accordance with the present invention, provision for attachment to the associated pump structure being indicated and the valve spool standing in the position that it assumes during the upstroke of the pistons, immediately after lower reversal.

FIG. 3 is a view similar to FIG. 2 with the valve spool stand ing in the position it assumes immediately after upper reversal at the downstroke of the pistons.

FIG. 4 is a perspective view showing the valve spool of the reverse valve assembly according to the present invention.

F IG. 5 is an enlarged cross-sectional view taken on the line 5-5 of FIG. 2.

FIG. 6 is a central vertical sectional view with parts broken away of a hydraulic motor having a modified reverse valve assembly constructed in accordance with the present invention wherein the exhaust passage, and thus discharge, is through the valve spool and out the top, the valve spool standing in the position that it assumes during the upstroke of the pistons, immediately after lower reversal.

FIG. 7 is a view similar to FIG. 6, with the valve spool standing in the position that it assumes during the downstroke of the pistons, immediately after upper reversal.

DESCRlPTlON OF THE PREFERRED EMBODIMENTS The downwell pump unit 10 includes an outer casing 12 which has been divided by the packer 14 into an upper engine section 16 and a lower pump section 18, which is broken away except for its extreme upper end. A source of operating fluid under pressure, which may be oil or water, from the surface is introduced into the engine section 16 from a fitting having a central passage 20 which may be threaded into a conventional swab nose section in the case of a free pump or may receive a macaroni string in the case of a fixed pump as is well known in the art.

An engine cylinder 22 is carried within the engine section 16 and the annular space 24 between the engine cylinder 22 and the casing 12 receives either operating fluid from the passage 20, and thus forms an operating fluid supply passage for the hydraulic engine, or communicates with the exhaust or discharge passage. For example, the annular spaces 24a and 24b continuously receive operating fluid under pressure, while the annular space 240 provides an exhaust or discharge passage.

Upper, center and lower engine pistons 26, 28 and 30 are carried for reciprocation within the engine cylinder 22 and are connected by a rod 32 to one or more pump pistons or plungers (not shown) by a threaded connection 35, in the usual manner. The space 36 adjacent the threaded connection 35 is constantly at discharge pressure and in communication with the surface through passages that are not shown. This space is used, therefore, to accept fluid discharged by the pump.

At this point it should be noted that the engine pistons, 26, 28 and 30 are of. the differential area type, whereby equal operating pressures on the two faces of each piston cause movement thereof in one direction. Additionally, it should be noted that a chamber 33 is provided within the engine cylinder 22 above the upper piston 26. The chamber 33 communicates with the various cylinders in which the pistons 26, 28 and 30 reciprocate, and as it is alternately pressurized and exhausted, the engine is caused to reciprocate. This in turn reciprocates the pump plungers (not shown) in the lower pump section 18, causing oil to be pumped from the well.

The reverse valve assembly includes an elongated tubular valve spool 34 having first, second and third lands 36, 38 and 40, respectively, the second land 38 being the larger of the three. The valve spool is longitudinally displaced from the uppermost one of the engine pistons 26 and mounted for reciprocal movement in the valve housing 23. The valve spool 34 is provided with a first annulus 42 between the first and second lands 36 and 38 and with a second annulus 44 between the second and third lands 38 and 40. As can be seen, the first annulus 42 is approximately twice the area of the second annulus 44 It will be clear that due to the fact that the second annulus 44 is always in communication with the operating fluid, as well as to the fact that the second land 38 is the largest of the three, an upward force on the spool 34 results. However, the second annulus 44 is approximately half the area of the first annulus 42. Accordingly, whenever the annulus 42 is pressurized, the upward force resulting from the operating fluid in the annulus 44 is overcome and the valve spool 34 is urged down. Likewise, when the annulus 42 is exhausted, the upward force in the annulus 44 becomes dominant and the valve spool 34 moves up.

At this point it should be noted that the interior 35 of the valve spool 34 is always in communication with the exhaust passage or discharge. The purpose of such communication will be more fully explained hereinafter.

Port means 52 communicate with the chamber 33 and thus with the area above the uppermost one of the engine piston 26. As will also be more fully explained hereinafter, the port means 52 alternately connect the chamber 33 with the second annulus 44 and with the interior of the valve spool 35.

A longitudinal pilot rod 54 extends through the valve spool 34 and is attached to the uppermost engine piston 26 for movement therewith. As can be seen, the pilot rod moves within the sleeves 56, 58, 60 and 62, which are positioned within the valve housing 23. More particularly, the sleeves 56 and 58 help to define a chamber 64 within the valve housing 23 which communicates with the first annulus 42, the sleeves 58 and 60 help to define the chamber 66 in which the valve spool 34 reciprocates, and the sleeve 62 is mounted within the chamber 33 which is above the upper piston 26.

The pilot rod,54 is provided with three sets of spaced apart ports, which are preferably radial ports, 46, 48 and 50 therein, the sets of ports being interconnected through the passage means 51. As can be seen, when the pilot rod 54 reciprocates, the first set of ports 46 move between communication with the operating fluid which is always above the sleeve 56 and with the chamber 64 which communicates with the first annulus 42 of the valve spool 34. Likewise, the second set of ports 48 moves between communication with the chamber 64 which communicates with the first annulus 42 and with the interior 35 of the valve spool 34. Additionally, the third set of ports 50 move from a first closed position in the sleeve 60 through an open position in communication with the chamber 33 above the uppermost engine piston 26 to a second closed position in the sleeve 62. It should, perhaps, be noted that the open position of the sets of ports 50 in communication with the chamber 33 results when the third set of ports 50 travels through the bore 68 which is provided with ports 70 communicating with the chamber 33.

In operation, the downstroke begins, of course, with the spool 34 in its lowermost position. When the spool 34 is in this position, the first set of ports 46 communicate with the operating fluid above the sleeve 56, whereupon the operating fluid proceeds through the passage 51 in the pilot rod 54 and into the chamber 64 which communicates with the first annulus 42. As was heretofore explained, when the first annulus 42 is pressurized, it overcomes the upward force of the spool 34 resulting from the operating fluid which is continuously in the second annulus 44. During the downward movement of the valve spool 34 to its lowermost position, it traverses the port means 52 and connects the chamber 33 with the second annulus 44. This, of course, pressurizes the chamber 33 with operating fluid and causes the engine pistons 26, 28 and 30, or the traveling assembly to move downwardly.

Referring now to FIG. 2, which shows the valve spool 34 standing in the position it assumes during the upstroke of the piston, ancl specifically, immediately after down or lower reversal, it will be seen that the second set of ports 48 in the pilot rod 54 have moved below the sleeve 58, thereby establishing communication through the first set of ports 46 and chamber 64. The first annulus 42 is now vented to exhaust or discharge pressure and the valve spool has moved up. lt should be noted that immediately priorto the second set of ports 48 emerging from the sleeve 58, the third set of ports 50 enter the sleeve 62 to shut off communication with the chamber 33. The port means 52 having been traversed by the third land 40 on the valve spool 34 connects the chamber 33 above the upper piston 26 with the interior 35 of the valve spool 34, and thus with discharge. Then this, of course, causes the pressure in the chamber 33 to become exhaust and the traveling assembly begins to move up. As the second set of ports 48 are withdrawn into the sleeve 58, the third set of ports 50 come out of the sleeve 62 and exhaust pressure is main-- tained on the first annulus 42 so that the upward force in the second annulus 44 keeps the valve spool 34 up. Escape of leakage into the annulus 42 is assured through the passage 51 in the pilot rod 54 and into the chamber 33 above the area of the upper piston 26 until the third set of ports 50 are drawn into the sleeve 60.

Immediately after the third set of ports 50 are shut off or closed within the sleeve 60, the first set ofports 46 move into communication with the operating fluid above the sleeve 56. Operating fluid enters the chamber 64 through the second set of ports 48 and thence to the first annulus 42 to move the valve spool 34 down. The third land 40 of the valve spool 34 traverses the port means 52 and the chamber 33 is now in communication with operating fluid to effect a downstroke of the traveling assembly. Thereafter as the first set of ports 46 are withdrawn from the operating fluid above the sleeve 56, the third set of ports 50 emerge from the sleeve 60 into the chamber 33. Drift of the valve spool 34 is prevented by sup plementing the leakage out of the first annulus 42 by operating fluid from the chamber 33, through the third set of ports 50 and the passage means 51 and through the second set of ports 48 into the chamber 64 and thus to the first annulus 42.

FIGS. 6 and 7 show central vertical sectional views with parts broken away through a hydraulic motor having a modified reverse valve assembly wherein the exhaust passage, and thus discharge, is through the valve spool 34 and out the top of the hydraulic pump, as opposed to where the exhaust passage, and thus discharge, is out the bottom of the hydraulic motor as shown in FIGS. 2 and 3.

At this time it should be emphasized that the operation of the reverse valve assembly shown in FIGS. 6 and 7 is identical with its operation as disclosed in FIGS. 1 and 2 and that corresponding reference numerals have been utilized. There are, of course, certain modifications present in the unit of FIGS. 6 and 7, which are necessary so that this unit will accommodate discharge out of the top thereof, such as, for example, the shape of the chamber 66 within the valve housing 23 within which the valve spool 34 reciprocates. However, for purposes of clarity such modifications have been designated by utilizing the subscript a."

In general, it should be noted that when the escape passage or discharge is through the top of the unit, the annular space 24 between the engine cylinder 22 and the outer casing 12 continually communicates with the operating fluid and with the second annulus 44 in the valve spool 34a. In other words, no portion of the annular space 24 communicates with the exhaust passage or discharge, as is done by that portion 24c thereof shown in FIGS. 2 and 3.

It should be emphasized that as used throughout this application, the terms up" and down," and other forms thereof such as upwardly," downwardly," upstroke and downstroke," relate to the orientation of the several embodiments described and are not limitations to be interpreted as limiting the invention to such position or direction.

It will be seen that the present invention provides a simple, effective reverse valve assembly which is extremely positive in holding the valve spool in position until ready to switch. some leakage may be tolerated across the second land 38 of the valve spool, and the valve will, in general, also tolerate more imbalance, wear and contamination than prior art valves. Additionally, the reverse valve of the present invention allows the reversal cycles to go up markedly at the same time it achieves a positive reversal. For example, oscilloscope traces show about 0.01 seconds for reversal of the valve spool of the present invention, versus about 0.02 seconds for related prior art valves.

While the invention has been disclosed in conjunction with a specific form and disposition of the parts, it will, of course, be appreciated that numerous modifications and changes can be made therein without departing from the scope of the appended claims.

The embodiments of the invention in which I claim an exclusive property or privilege are defined as follows:

1. in a fluid-operated downwell pump of the type having a pump cylinder, an engine cylinder longitudinally displaced from the pump cylinder, connected pistons operating in the respective pump and engine cylinders, said engine pistons being of the differential area type, whereby equal operating pressures on the two faces of each engine piston cause movement thereof in one direction, an exhaust passage, and a source of operating fluid under pressure, the improvement, in combination therewith, comprising a reverse valve assembly including an elongated tubular valve spool longitudinally disposed from the uppermost engine piston and mounted for reciprocal movement in a valve housing in said engine cylinder, said valve spool being provided with lands thereon defining annuli which communicate with said operating fluid and with said exhaust passage, the interior of said valve spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost engine piston and alternately connecting said area with at least one of said annuli and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with sets of spaced apart ports therein interconnected through passage means, said sets of ports moving between communication with said operating fluid in communication with one of said annuli, between communication with one of said annuli and communication with the interior of said valve spool, and between a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocate s, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said valve spool is moved back and forth in said valve housing, one of the lands thereof alternately connects said port means, and thus the area above said uppermost engine piston, with one of said annuli and the interior of said valve spool, and alternately pressurizes and exhausts the area above said uppermost engine piston, thereby causing said engine to reciprocate.

2. The downwell pump according to claim 1, wherein said valve spool is provided with first, second and third lands, said second land being the larger of the three, said valve spool having a first annulus between said first and second lands, and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, and said second annulus always being in communication with said operating fluid, and wherein said port means alternately connects said area above said uppermost engine piston with said second annulus and with the interior of said valve spool.

3. The downwell pump according to claim 2, wherein said longitudinal pilot rod is provided with three sets of spaced apart ports therein, said first set of ports moving between 'communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, and as said valve spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and the interior of said spool.

4. The downwell pump according to claim 3, wherein said pilot rod moves within a plurality of longitudinally spaced sleeves positioned within said valve housing.

5. The downwell pump according to claim 4, wherein said pilot rod moves within first, second, third and fourth sleeves, said first and second sleeves helping to define a first chamber within said valve housing which communicates with said first annulus, said second and third sleeves helping to define a second chamber within said valve housing in which said valve spool reciprocates, and said fourth sleeve being mounted within a third chamber above said upper piston, said sleeves and said sets of spaced ports being positioned such that as said pilot rod reciprocates, said first set of ports move between communication with said operating fluid and with said first chamber, said second set of ports moves between communication with said first chamber and with the interior of said valve spool, and said third set of ports moves from a first closed position within said third sleeve through an open position in communication with said third chamber to a second closed position within said fourth sleeve.

6. A reverse valve assembly for a fluid-operated downwcll pump having a pump cylinder, an engine cylinder longitudinally displaced from said pump cylinder, connected pistons operating in the respective pump and engine cylinders, each said engine piston having a greater effective area on one side than on the other, whereby equal operating pressures on the two faces of each engine piston cause movement thereof in one direction, an escape passage, and a source of operating fluid under pressure, said reverse valve assembly comprising an elongated tubular valve spool longitudinally disposed from the uppermost engine piston and mounted for reciprocal movement in a valve housing in said engine cylinder, said valve spool being provided with lands thereon defining annuli which communicate with said operating fluid and with said exhaust passage, the interior of said valve spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost engine piston and alternately connecting said area with at least one of said annuli and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with sets of spaced apart ports therein connected through passage means, said sets of ports moving between communication with said operating fluid in communication with one of said annuli, between communication with one of said annuli and communication with the interior of said valve spool, and between a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said valve spool is moved back and forth in said valve housing, one of the lands thereof alternately connects said port means, and thus the area above said uppermost engine piston, with one of said annuli and the interior of said valve spool, and alternately pressurizes and exhausts-the area above said uppermost engine piston, thereby causing said engine to reciprocate.

7. The reverse valve assembly according to claim 6, wherein said valve spool is provided with first, second and third lands, said second land being the larger of the three, said valve spool having a first annulus between said first and second lands, and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, and said second annulus always being in communication with said operating fluid, and wherein said port means alternately connects said area above said uppermost engine piston with said second annulus and with the interior of said valve spool.

8. The reverse valve assembly according to claim 7', wherein said longitudinal pilot rod is provided with three sets of spaced apart ports therein, said first set of ports moving between communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, and as said valve spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and the interior of said spool.

9. The reverse valve assembly according to claim 8, wherein said pilot rod moves within a plurality of longitudinally spaced sleeves positioned within said valve housing.

10. The reverse valve assembly according to claim 9, wherein said pilot rod moves within first, second, third and fourth sleeves, said first and second sleeves helping to define a first chamber within said valve housing which communicates with said first annulus, said second and third sleeves helping to define a second chamber within said valve housing in which said valve spool reciprocates, and said fourth sleeve being mounted within a third chamber above said upper piston, said sleeves and said sets of spaced ports being positioned such that as said pilot rod reciprocates, said first set of ports move between communication with said operating fluid and with said first chamber, said second set of ports moves between communication with said first chamber and with the interior of said valve spool, and said third set of ports moves from a first closed position within said third sleeve through an open position in communication with said third chamber to a second closed position within said fourth sleeve.

11. In a hydraulic engine having a cylinder, at source of power fluid, a discharge, and at least one piston slidable in said cylinder, said piston having a greater effective area on one side than on the other, whereby equal operating pressures on its two faces cause movement thereof in one direction, a reverse valve assembly comprising an elongated tubular valve spool longitudinally disposed from the uppermost engine piston and mounted for reciprocal movement in avalve housing in said engine cylinder, said valve spool being provided with lands thereon defining annuli which communicate with said operating fluid and with said exhaust passage, the interior of said valve spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost enginepiston and alternately connects ing said area with at least one of said annuli and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with sets of spaced apart ports therein interconnected through passage means, said sets of ports moving between communication with said operating fluid in communication with one of said annuli, between communication with one of said annuli and communication with the interior of said valve spool, and between a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said valve spool is moved back and forth in said valve housing, one of the lands thereof alternately connects said port means, and thus the area above said uppermost engine piston, with one of said annuli and the interior of said valve spool, and alternately pressurizes and exhausts the area above said uppermost engine piston, thereby causing said engine to reciprocate.

12. The hydraulic engine according to claim ll, wherein said valve spool is provided with first, second and third lands, said second land being the larger of the three, said valve spool having a first annulus between said first and second lands, and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, and said second annulus always being in communication with said operating fluid, and wherein said port means alternately connects said area above said uppermost engine piston with said second annulus and with the interior of said valve spool.

13. The hydraulic engine according to claim 12, wherein said longitudinal pilot rod is provided with three sets of spaced apart ports therein, said first set of ports moving between communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot reciprocates, and as said valve spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and the interior of said spool.

14. The hydraulic engine according to claim 13, wherein said pilot rod moves within a plurality of longitudinally spaced sleeves positioned within said valve housing.

15. The hydraulic engine according to claim 34, wherein said pilot rod moves within first, second, third and fourth sleeves, said first and second sleeves helping to define a first chamber within said valve housing which communicates with said first annulus, said second and third sleeves helping to define a second chamber within said valve housing in which said valve spool reciprocates, and said fourth sleeve being mounted within a third chamber above said upper piston, said sleeves and said sets of spaced ports being positioned such that as said pilot rod reciprocates, said first set of ports move between communication with said operating fluid and with said first chamber, said second set of ports moves between communication with said first chamber and with the interior of said valve spool, and said third set of ports moves from a first closed position within said third sleeve through an open position in communication with said third chamber to a second closed position within said fourth sleeve.

16. In a fluid-operated downwell pump of the type having a pump cylinder, an engine cylinder longitudinally displaced from said pump cylinder, connected pistons operating in the respective pump and engine cylinders, said engine pistons being of the differential area type, whereby equal operating pressures on the two faces of each engine piston cause movement thereof in one direction, an exhaust passage, and a source of operating fluid under pressure, the improvement, in combination therewith, comprising a reverse valve assembly including an elongated tubular valve spool having first, second and third lands, said second land being the larger of the three, said valve spool being longitudinally displaced from the uppermost one of said engine pistons and mounted for reciprocal movement in a valve housing in said engine cylinder, said valve spool having a first annulus between said first and second lands and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, said annulus always being in communication with said operating fluid and the interior of said spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost engine piston and alternately connecting said area with said second annulus and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with three sets of spaced apart ports therein, said sets of ports being interconnected through passage means, said first set of ports moving between communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said valve spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and with the interior of said valve spool, and alternately pressurizes and exhausts the area above said uppermost engine piston, thereby causing said engine to reciprocate.

17. A reverse valve assembly for a fluid-operated downwell pump having a pump cylinder, an engine cylinder longitudinally displaced from said pump cylinder, connected pistons operating in the respective pump and engine cylinders, each said engine piston having a greater effective area on one side than on the other, whereby equal operating pressures on the two faces of each engine piston cause movement thereof in one direction, an escape passage, and a source of operating fluid under pressure, said reverse valve assembly comprising an elongated tubular valve spool having first, second, and third lands, said second land being the largest of the three, said valve spool being longitudinally displaced from the uppermost one of said engine pistons and mounted for reciprocal movement in a valve housing in said engine cylinder, said valve spool having a first annulus between said first and second lands and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, said second annulus always being in communication with said operating fluid and the interior of said spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost engine piston and alternately connecting said area with said second annulus and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with three sets of spaced apart ports therein, said sets of ports being interconnected through passage means, said first set of ports moving between communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and with the interior of said valve spool, and alternately pressurizes and exhausts the area above said uppermost engine piston, thereby causing said engine to reciprocate.

18. In a hydraulic engine having a cylinder, a source of power fluid, a discharge, and at least one piston slidable in said cylinder, said piston having a greater efi'ective area on one side than on the other, whereby equal operating pressures on its two faces cause movement thereof in one direction, a reverse valve assembly comprising an elongated tubular valve spool having first, second and third lands, said second land being the largest of the three, said valve spool being longitudinally displaced from said piston and mounted for reciprocal movement in a valve housing in said cylinder, said valve spool having a first annulus between said first and second lands and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, said second annulus always being in communication with said power fluid and the interior of said spool always being in communication with said discharge; port means communicating with the area above said piston and alternately connecting said area with said second annulus and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said piston for movement therewith, said pilot rod being provided with three sets of spaced apart ports therein, said sets of ports being interconnected through passage means, said first set of ports moving between communication with said power fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said 

1. In a fluid-operated downwell pump of the type having a pump cylinder, an engine cylinder longitudinally displaced from the pump cylinder, connected pistons operating in the respective pump and engine cylinders, said engine pistons being of the differential area type, whereby equal operating pressures on the two faces of each engine piston cause movement thereof in one direction, an exhaust passage, and a source of operating fluid under pressure, the improvement, in combination therewith, comprising a reverse valve assembly including an elongated tubular valve spool longitudinally disposed from the uppermost engine piston and mounted for reciprocal movement in a valve housing in said engine cylinder, said valve spool being provided with lands thereon defining annuli which communicate with said operating fluid and with said exhaust passage, the interior of said valve spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost engine piston and alternately connecting said area with at least one of said annuli and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with sets of spaced apart ports therein interconnected through passage means, said sets of ports moving between communication with said operating fluid in communication with one of said annuli, between communication with one of said annuli and Communication with the interior of said valve spool, and between a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said valve spool is moved back and forth in said valve housing, one of the lands thereof alternately connects said port means, and thus the area above said uppermost engine piston, with one of said annuli and the interior of said valve spool, and alternately pressurizes and exhausts the area above said uppermost engine piston, thereby causing said engine to reciprocate.
 2. The downwell pump according to claim 1, wherein said valve spool is provided with first, second and third lands, said second land being the larger of the three, said valve spool having a first annulus between said first and second lands, and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, and said second annulus always being in communication with said operating fluid, and wherein said port means alternately connects said area above said uppermost engine piston with said second annulus and with the interior of said valve spool.
 3. The downwell pump according to claim 2, wherein said longitudinal pilot rod is provided with three sets of spaced apart ports therein, said first set of ports moving between communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, and as said valve spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and the interior of said spool.
 4. The downwell pump according to claim 3, wherein said pilot rod moves within a plurality of longitudinally spaced sleeves positioned within said valve housing.
 5. The downwell pump according to claim 4, wherein said pilot rod moves within first, second, third and fourth sleeves, said first and second sleeves helping to define a first chamber within said valve housing which communicates with said first annulus, said second and third sleeves helping to define a second chamber within said valve housing in which said valve spool reciprocates, and said fourth sleeve being mounted within a third chamber above said upper piston, said sleeves and said sets of spaced ports being positioned such that as said pilot rod reciprocates, said first set of ports move between communication with said operating fluid and with said first chamber, said second set of ports moves between communication with said first chamber and with the interior of said valve spool, and said third set of ports moves from a first closed position within said third sleeve through an open position in communication with said third chamber to a second closed position within said fourth sleeve.
 6. A reverse valve assembly for a fluid-operated downwell pump having a pump cylinder, an engine cylinder longitudinally displaced from said pump cylinder, connected pistons operating in the respective pump and engine cylinders, each said engine piston having a greater effective area on one side than on the other, whereby equal operating pressures on the two faces of each engine piston cause movement thereof in one direction, an escape passage, and a source of operating fluid under pressure, said reverse valve assembly comprising an elongated tubular valve spool longitudinally disposed from the uppermost engine piston and mOunted for reciprocal movement in a valve housing in said engine cylinder, said valve spool being provided with lands thereon defining annuli which communicate with said operating fluid and with said exhaust passage, the interior of said valve spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost engine piston and alternately connecting said area with at least one of said annuli and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with sets of spaced apart ports therein connected through passage means, said sets of ports moving between communication with said operating fluid in communication with one of said annuli, between communication with one of said annuli and communication with the interior of said valve spool, and between a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said valve spool is moved back and forth in said valve housing, one of the lands thereof alternately connects said port means, and thus the area above said uppermost engine piston, with one of said annuli and the interior of said valve spool, and alternately pressurizes and exhausts the area above said uppermost engine piston, thereby causing said engine to reciprocate.
 7. The reverse valve assembly according to claim 6, wherein said valve spool is provided with first, second and third lands, said second land being the larger of the three, said valve spool having a first annulus between said first and second lands, and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, and said second annulus always being in communication with said operating fluid, and wherein said port means alternately connects said area above said uppermost engine piston with said second annulus and with the interior of said valve spool.
 8. The reverse valve assembly according to claim 7, wherein said longitudinal pilot rod is provided with three sets of spaced apart ports therein, said first set of ports moving between communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, and as said valve spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and the interior of said spool.
 9. The reverse valve assembly according to claim 8, wherein said pilot rod moves within a plurality of longitudinally spaced sleeves positioned within said valve housing.
 10. The reverse valve assembly according to claim 9, wherein said pilot rod moves within first, second, third and fourth sleeves, said first and second sleeves helping to define a first chamber within said valve housing which communicates with said first annulus, said second and third sleeves helping to define a second chamber within said valve housing in which said valve spool reciprocates, and said fourth sleeve being mounted within a third chamber above said upper piston, said sleeves and said sets of spaced ports being positioned such that as said pilot rod reciprocates, said first set of ports move between communication with said operating fluid and with said first chamber, said second set of ports moves between communication with said first chamber and with the interior of said valve spool, and said third set of ports moves from a first closed position within said third sleeve through an open position in communication with said third chamber to a second closed position within said fourth sleeve.
 11. In a hydraulic engine having a cylinder, a source of power fluid, a discharge, and at least one piston slidable in said cylinder, said piston having a greater effective area on one side than on the other, whereby equal operating pressures on its two faces cause movement thereof in one direction, a reverse valve assembly comprising an elongated tubular valve spool longitudinally disposed from the uppermost engine piston and mounted for reciprocal movement in a valve housing in said engine cylinder, said valve spool being provided with lands thereon defining annuli which communicate with said operating fluid and with said exhaust passage, the interior of said valve spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost engine piston and alternately connecting said area with at least one of said annuli and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with sets of spaced apart ports therein interconnected through passage means, said sets of ports moving between communication with said operating fluid in communication with one of said annuli, between communication with one of said annuli and communication with the interior of said valve spool, and between a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said valve spool is moved back and forth in said valve housing, one of the lands thereof alternately connects said port means, and thus the area above said uppermost engine piston, with one of said annuli and the interior of said valve spool, and alternately pressurizes and exhausts the area above said uppermost engine piston, thereby causing said engine to reciprocate.
 12. The hydraulic engine according to claim 11, wherein said valve spool is provided with first, second and third lands, said second land being the larger of the three, said valve spool having a first annulus between said first and second lands, and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, and said second annulus always being in communication with said operating fluid, and wherein said port means alternately connects said area above said uppermost engine piston with said second annulus and with the interior of said valve spool.
 13. The hydraulic engine according to claim 12, wherein said longitudinal pilot rod is provided with three sets of spaced apart ports therein, said first set of ports moving between communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot reciprocates, and as said valve spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and the interior of said spool.
 14. The hydraulic engine according to claim 13, wherein said pilot rod moves within a plurality of longitudinally spaced sleeves positioned within said valve housing.
 15. The hydraulic engine according to claim 14, wherein said pilot rod moves within first, second, third and fourth sleeves, said first and second sleeves helping to define a first chamber within said valve housing which communicates with said first annulus, said second and third sleeves helping to define a second chamber within said valve housing in which said valve spool reciprocates, and said fourth sleeve being mounted within a third chamber above said upper piston, said sleeves and said sets of spaced ports being positioned such that as said pilot rod reciprocates, said first set of ports move between communication with said operating fluid and with said first chamber, said second set of ports moves between communication with said first chamber and with the interior of said valve spool, and said third set of ports moves from a first closed position within said third sleeve through an open position in communication with said third chamber to a second closed position within said fourth sleeve.
 16. In a fluid-operated downwell pump of the type having a pump cylinder, an engine cylinder longitudinally displaced from said pump cylinder, connected pistons operating in the respective pump and engine cylinders, said engine pistons being of the differential area type, whereby equal operating pressures on the two faces of each engine piston cause movement thereof in one direction, an exhaust passage, and a source of operating fluid under pressure, the improvement, in combination therewith, comprising a reverse valve assembly including an elongated tubular valve spool having first, second and third lands, said second land being the larger of the three, said valve spool being longitudinally displaced from the uppermost one of said engine pistons and mounted for reciprocal movement in a valve housing in said engine cylinder, said valve spool having a first annulus between said first and second lands and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, said annulus always being in communication with said operating fluid and the interior of said spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost engine piston and alternately connecting said area with said second annulus and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with three sets of spaced apart ports therein, said sets of ports being interconnected through passage means, said first set of ports moving between communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said valve spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and with the interior of said valve spool, and alternately pressurizes and exhausts the area above said uppermost engine piston, thereby causing said engine to reciprocate.
 17. A reverse valve assembly for a fluid-operated downwell pump having a pump cylinder, an engine cylinder longitudinally displaced from said pump cylinder, connected pistons operating in the respective pump and engine cylinders, each said engine piston having a greater effective area on one side than on the other, whereby equal operating pressures on the two faces of each engine piston cauSe movement thereof in one direction, an escape passage, and a source of operating fluid under pressure, said reverse valve assembly comprising an elongated tubular valve spool having first, second, and third lands, said second land being the largest of the three, said valve spool being longitudinally displaced from the uppermost one of said engine pistons and mounted for reciprocal movement in a valve housing in said engine cylinder, said valve spool having a first annulus between said first and second lands and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, said second annulus always being in communication with said operating fluid and the interior of said spool always being in communication with said exhaust passage; port means communicating with the area above said uppermost engine piston and alternately connecting said area with said second annulus and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said uppermost engine piston for movement therewith, said pilot rod being provided with three sets of spaced apart ports therein, said sets of ports being interconnected through passage means, said first set of ports moving between communication with said operating fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said uppermost engine piston to a second closed position, respectively, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means, and thus the area above said uppermost engine piston, with said second annulus and with the interior of said valve spool, and alternately pressurizes and exhausts the area above said uppermost engine piston, thereby causing said engine to reciprocate.
 18. In a hydraulic engine having a cylinder, a source of power fluid, a discharge, and at least one piston slidable in said cylinder, said piston having a greater effective area on one side than on the other, whereby equal operating pressures on its two faces cause movement thereof in one direction, a reverse valve assembly comprising an elongated tubular valve spool having first, second and third lands, said second land being the largest of the three, said valve spool being longitudinally displaced from said piston and mounted for reciprocal movement in a valve housing in said cylinder, said valve spool having a first annulus between said first and second lands and a second annulus between said second and third lands, said first annulus being approximately twice the area of said second annulus, said second annulus always being in communication with said power fluid and the interior of said spool always being in communication with said discharge; port means communicating with the area above said piston and alternately connecting said area with said second annulus and with the interior of said valve spool; and a longitudinal pilot rod extending through said valve spool and attached to said piston for movement therewith, said pilot rod being provided with three sets of spaced apart ports therein, said sets of ports being interconnected through passage means, said first set of ports moving between communication with said power fluid and communication with said first annulus, said second set of ports moving between communication with said first annulus and communication with the interior of said valve spool, and said third set of ports moving from a first closed position through an open position in communication with the area above said piston to a second closed position, respectivelY, as said pilot rod reciprocates, whereby the signal for movement of said valve spool is provided through said sets of ports in said pilot rod, and as said valve spool is moved back and forth in said valve housing, said third land thereof alternately connects said port means and thus the area above said piston with said second annulus and with the interior of said valve spool, and alternately pressurizes and exhausts the area above said piston, thereby causing said engine to reciprocate. 